萊頓溫標

萊頓標度 (°L) 在20世紀初通過提供氦蒸氣壓的常規值來校準低溫間接測量值。

萊頓標度可在-183°C以下使用，這也是1930年代國際溫標的起點（Awbery 1934）。

參考資料 

Berman, A.; Zemansky, M. W.; and Boorse, H. A.; Normal and Superconducting Heat Capacities of Lanthanum, Physical Review, Vol. 109, No. 1 (January 1958), pp. 70–76. Quote:
« The 1955 Leiden scale13 was used to convert helium vapor pressures into temperatures [...] (13) H. van Dijk and M. Durieux, in Progress in Low Temperature Physics II, edited by C. J. Gorter (North-Holland Publishing Company, Amsterdam, 1957), p. 461. In the region of calibration the 1955 Leiden scale, TL55, differs from the Clement scale, T55E, by less than 0.004 deg. » (emphasis added)
Grebenkemper, C. J.; and Hagen, John P.; The Dielectric Constant of Liquid Helium, Physical Review, Vol. 80, No. 1 (October 1950), pp. 89–89. Quote:
 « The temperature scale used was the 1937 Leiden scale. » (emphasis added)
Awbery, J. H.; Heat, Rep. Prog. Phys. 1934, No. 1, pp. 161–197 . Quote:
 « It should be mentioned that below -183°C, the Leiden workers do not entirely agree with some of the other cryogenic laboratories, but use a scale of their own, generally known as the Leiden scale. » (emphasis added)

溫度單位